1. Field of the Invention
The present invention generally relates to line clamping devices and, more specifically, to a high tension line clamp with a quick release mechanism.
2. Description of the Prior Art
It is frequently necessary to control a line by either arresting or stopping its motion or releasing it. On sailing vessels, for example, lines are used to raise and control sails and other operating units often under heavy loads. The same line may first be lightly loaded, and then as the tension required increases, the use of a winch is necessary. To allow one winch to be used for several lines, of the same or varying sizes, a sheet or line stopper is provided for each line. When out of engagement, the line stopper permits the line to run in both directions. In an engaged position, the line runs under light pressure in one direction only. It is therefore possible to haul a line in by hand without slipping as a self-locking action prevents line movement of the line in the opposite direction. As the load increases, a winch is used to set the line in the desired position as control becomes difficult by hand. With the line stoppers presently available, although the line may be taken off the winch and still be held by the line stopper, it is impossible to release the line without the use of a winch to hold the load while the line stopper is released. In sailboat racing, putting a line on a winch in order to effect a release of the line stopper is time consuming as well as tying up a winch which may be necessary for another control function. Also, the line stopper tends to contact and abrade a line on its release under load even using a winch to help effect such a release.
The prior art is replete with braking mechanisms for arresting or releasing a line under tension. As suggested, such lines are frequently used to hoisting and trimming of sails in which the line may be subjected to tensions ranging from low to extremely high tensions up to and even exceeding ten tons.
A common mechanism for arresting a line includes a cylindrical surface mounted to exhibit an eccentric braking surface in relation to a fixed abutment surface so that movement of the eccentric braking surface can vary or adjust a gap through which the line is guided. When the gap is sufficiently reduced, the line is wedged between the braking and abutment surfaces. Normally, continued tension on the line in the same direction increases the wedging effect and thereby the lock on the line. One example of such a rope holding device is disclosed in U.S. Pat. No. 3,835,507, which shows a cylindrical cam mounted for rotation on a pin to cause the circumferential gripping surface to provide a variable line gap when the cam is rotated. A U-shaped base member having legs with a pivot pin mounted therein is adapted to be anchored on a sailboat. A cam mechanism includes an inner element having a handle attached thereto which is eccentrically mounted for pivotal movement around the pivot pin. A movable outer element is positioned for pivotal movement and a rotational movement on the eccentrically mounted inner element. One or more springs are mounted between the inner and outer elements of the cam mechanism which are acted on when relative movement takes place between the elements. The spring is compressed when the handle is pivoted placing the outer member in locking engagement with the line in the load direction which locking action is increased with increasing load; while allowing the outer member to rotate or float over the line in the other direction. Each release of the load direction is effected by raising the handle. The line stopper can be released under heavy load because the outer element holding the line rotates in the same direction the line is running, the line will not be abraded thereby limiting line wear. The line stopper may be mounted either vertically or horizontally.
A disadvantage of existing rope holding or stopping devices is that they require substantial forces to be applied to release the line after it has been locked. Thus, once the line tension causes the eccentric cam surface to close a gap for the line and wedges it to stop it and lock it continued tension on the line in the same direction tends to decrease the gap even further with attendant increased holding pressure on the line. Releasing the line from its wedged condition can be effected by reversing the process and increasing the size of the gap through which the line extends. Clearly, this can be done in one of two ways. One or the other of the wedging surfaces must be moved away from the other opposing surface so that the gap is increased and the line is again permitted to move. As suggested, the prior art devices have typically used a fixed abutment surface that always remains stationary. Therefore, the only way to increase the gap is to move the surface on the eccentric cam in a direction opposite to the initial direction that caused the cam to lock the line. However, this is not always an easy or quick task. The reason for this is that the tension in the line can be so high that applying an opposing tension on the other end of the line may be difficult if manually attempted. Application of a tension greater than the tension at the opposing end of the line could rotate the eccentric cam in the releasing position with attendant increase in the gap. This approach, however, becomes impractical when the tensions in the line are extremely high. For this reason, a winch must at times be used to overcome very high tensions in the line in order to reverse the direction of movement of the eccentric cam surface and thereby the size of the line receiving gap. In some cases, a handle or lever is used that is attached to the eccentric cam that allows a user to obtain mechanical advantage in moving or rotating the eccentric cam to an unlocking position. See, for example, U.S. Pat. No. 4,425,862 for a sail line stopper that uses a handle that cooperates with the cam. Unlocking the line using the stopper still requires significant effort.